Controlling spray guns

ABSTRACT

A spray gun for coating surfaces of a succession of articles of different shapes and sizes has the position of emission of liquid therefrom maintained substantially at a predetermined distance from the surface being sprayed by a variable profile cam the profile of which is automatically varied by adjusting means operable under control of control means which in turn is controlled by sensing devices located along the path of the article and which are arranged to sense the shape and size of the article.

O United States Patent 1191 1111 3,724,415 Knight 1451 Apr. 3, 1973 [54]CONTROLLING SPRAY GUNS 2,321,982 6/1943 Brackett ..118/323 [75]Inventor: Howard Richard James Knight, 52:; Hampton, England 3,594,2117/1971 Drum ..117/107.3 [73] Assignee: Carrier Engineering CompanyLimited, London England Primary Examuter-Mervm Ste1r 1 I AssistantExaminerLeo Mlllsteln [22] Flled: 1970 Attorney-Snyder and Butrum [21]A 1. No.: 67 868 pp 57 ABSTRACT [30] Foreign Application Priority Dataspray gun for coating surfaces of a success'ionof articles of differentshapes and s1zes has the pos1t1on of Sept-3,1969 Great 1311mm emissionof liquid therefrom maintained substantially at a predetermined distancefrom the surface being U.S. Cl prayed a variable profile cam the profileof 113/323 is automatically varied by adjusting means operable [51] Int.Cl. ..B05c 11/00, B05b 3/00 under control of control means which in turnis conl Field 0f Search trolled by sensing devices located along thepath of 117/1053, DIG 2 the article and which are arranged to sense theshape and size of the article. [56] References Cited 10 Claims, 9Drawing Figures UNITED STATES PATENTS 3,255,037 6/1966 Knight et al..118/2 Inventor PATENTEUAPM I973 SHEET 3 OF 4 Inventor CONTROLLINGSPRAY GUNS BACKGROUND OF THE INVENTION gun, and it may be used withparticular advantage in the spray coating of automobile bodies. I

In the mass production of automobile bodies it is frequently the casethat bodies of different styles follow one another through the spraycoating apparatus and, furthermore, as each body passes through thespraying apparatus it generally presents a succession of surfaces ofdifferent shapes and sizes to be sprayed. In addition to variations inthe general outlines of the bodies there are variations in the contoursof the bodies which it is generally necessary to follow in order toavoid unacceptable variations in the finish and thickness of thecoatings applied.

' transversely of the path of travel of the bodies, the

tracks having associated cam tracks following the body surfaces facingthem so that the guns as they are reciprocated follow the contours ofthe bodies.

Such known kinds of paint spraying apparatus have the disadvantage thatthey must be set up with the appropriate cams for each form of bodybeing coated, and they are not therefore capable of painting asuccession of bodies of differing contours.

The present invention relies upon the conception that, because thedistance from the contour of a body to the middle of a cord is not as arule critical, the contour of a body cam can be split up into separatechords joined together by generous curves.

SUMMARY According to the present invention there is provided anapparatus for coating surfaces of a succession of articles of differentshapes and sizes by a spray gun reciprocable along a path in a firstplane during movement of the surfaces past the gun along a path in asecond plane at right angles to said first plane, comprising sensingdevices located along the path of the articles and operable to sense theshape and size of the article, a variable profile cam operable tocontrol the movements of the gun in said first plane, cam profileadjusting means, and control means connected with said sensing devicesand said cam profile adjusting means and operable to actuate the camprofile adjusting means to adjust the profile of the cam according tothe form of the surface to be sprayed thereby during reciprocation ofthe spray gun to maintain the position of emission of liquid from thespray gun substantially at a predetermined distance from the surfacebeing sprayed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 diagrammatically shows a sideview of an automobile body, a spray coating apparatus and elements of abody form detecting device,

FIG. 2 shows a side view of an adjustable cam,

FIG. 3 shows an enlarged cross section on the line 3-3 of FIG. 2,

FIGS. 4 and 5 show side views of a further embodiment of adjustable camin different operating positions thereof,

FIG. 6 shows in block schematic form a circuit arrangement and adjustingmeans for adjusting the shape ofa cam as shown in FIG. 3, and

FIGS. 7, 8 and 9 show diagrammatic representations of a longitudinalsection through a spray gun guiding arrangement in different operatingpositions thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there isshown an automobile body 1 supported by a hanger or truck (not shown).The arrangement is such that bodies of different shape and sizefollowing consecutively may be handled.

The spraying apparatus includes a structure having two verticallydisposed side units 2, only one olwhich is shown, spaced apart one oneither side of the path of travel of the bodies, and a horizontallydisposed unit 3, above the path of travel of the bodies, for side sprayguns 4 and top spray guns 5. The spray guns 4 and 5 are reciprocablealong their units in first planes at right angles to a plane along whichmove the body surfaces which the spray guns are arranged to coat. Thelength of traverse of the side spray guns 4 is indicated by a slot 8 inthe casing of the vertical unit 2.

A plurality of photoelectric devices 9, 10, 11, 12 and 13, positionedlocal to thespray gun units, or in prior positions, that is before thespray booth in which spray,- ing is effected, are arranged to detect thepresence of a body or a particular part of a body and to provide signalsto a programming arrangement which controls the extent both of themovement of the spray guns along their respective units and the periodsof time during which spraying takes place, as described in US. Pat.specification No. 3,255,037, Knight et al.

It is, of course, necessary for there to be some movement of the guns inthe planes referred to, both towards and away from a body being sprayed,in order to follow the curve of the body and ensure an even coating. Thecontrol of this movement of the guns is generally by means of fixed camsand where a succession of bodies of different shape and size as seenfrom the side view, but with sides and tops presenting curves of similarshape as seen from the end view, is employed such an arrangement isquite satisfactory. However, when successive bodies havingcross-sectional profiles which differ considerably are employed or whenthe crosssectional profile varies considerably over the length of abody, such an arrangement employing a compromise shape of cam is notsatisfactory.

Referring to FIG. 2 there will now be described a variable profile camin its simplest form which is particularly suitable for use withapparatus of the kind described with reference to FIG. 1 in controllingthe movement of spray guns so that they may follow the profiles ofdifferent bodies with the position of emission of liquid therefrommaintained at a substantially predetermined distance from the surfacebeing sprayed. In FIG. 2 there is shown a first cam member 15 formedfrom a U-section channel member having two straight portions 16 and 17joined by a curved portion 18. The upper end 20 of the member 15 ismovable by means of a piston rod 21 from a pneumatically operated doubleacting cylinder 22. The lower end 23 of the member 15 is attached to abracket 24 which is pivoted about a fixed pivot 25 so that the arm 15can be rotated about the pivot 25 by the action of the cylinder 22 intoeither one of two positions, namely the position in which it is shownand the position indicated by the dotted line 15a.

There is also pivoted about the pivot 25, by means of a bracket 26, asecond cam member 27 formed as a straight member having a U-sectionchannel.

The lower end of the member 27 is attached to the piston rod 28 of adouble acting cylinder 30, which in turn is coupled to the piston of adouble acting cylinder 31, whereby the cam member 27 may be moved by theaction of the cylinders from the position shown into either of thepositions indicated by the dotted lines 27a and 27b. At the bases of theU-section channels 15 and 27 there is a cam profile-forming stripconsisting of a flexible steel strip 32 which extends lengthwise of thechannels 15, 27 and is maintained in tension by a coiled tension spring,indicated at 33. The strip 32 provides a cam profile within the members15 and 27 and continues as a curve between the ends of these members atthe brackets 24 and 26.

The cross-section shown in FIG. 3 makes clear the position of the strip32 within the member 15.

Referring to FIGS. 4 and there are shown first, second, and third cammembers 40, 41 and 42 formed from straight lengths of U-sectionchannels.

The second member 41 is coupled by arms 44 and 46 at its opposite endsto the ends of an arm 49 to form a unitary structure. The arms 44, 46extend in opposite directions at right angles to the second cam member41. The rocking arm 49 is pivoted about a fixed pivot point 50 and theopposite-ends of the rocking arm 49 carry pivots 45 and 48 about whichbrackets 43 and 47, attached to the ends of the first and third cammembers 40 and 42 respectively, may pivot. The second cam member 41 maybe positioned by rotation of the rocking arm 49 about the pivot 50either manually, by means of a pneumatically operated cylinder 51, or byany other rotatable means, acting on the rocking arm 49. Furthermore theunitary structure formed by the rocking arm 49, the arms 44 and 46 andthe second cam member 41 may, in a modified embodiment, be movedvertically by arranging the pivot 50 in a slot and acting on thestructure either by means of a remotely controlled pneumaticallyoperated cylinder (not shown) or manually. In a similar manner to thearrangement of FIG. 2, the end 52 of the third cam member 42 isconnected to the piston rod of a cylinder 53 which in turn is coupled tothe piston rod of a cylinder 54 and the end 55 of the first cam member40 is connected to the piston rod of a cylinder 56. There is also aflexible steel strip 57 passing along the bottom of the U-section cammembers 40, 41 and 42 and providing a cam profile within and between themembers. The strip 57 is maintained under tension by two coiled tensionsprings 58 and 59 at its opposite ends.

In addition to the straight cam profile which may be provided by thearrangement as shown in FIG. 5 and the arrangement as shown in FIG. 4,various possible other combinations of the positions of the first andthird cam members 40 and 42 are indicated at 40a, 42a, and 42b in FIG. 4for any one position of the second cam member 41 by rotating cam member41 about the pivot 50.

A control circuit arrangement determining the positioning of the cammembers will now be described with reference to FIG. 6 which shows aschematic diagram illustrating the five photoelectric devices 9, 10, 11,12 and 13 shown in FIG. 1 with their outputs applied to a number ofinputs of a control arrangement 61. The control arrangement includes, ineffect, a translator which may be based, for example, upon a diodematrix providing outputs upon leads 62, 63, 64 and 65 according to theinputs and a predetermined key. The outputs on the leads 63, 64, 65 and62 operate solenoid valves 66, 67, 68 and 69, which control the doubleacting cylinders 22, 30, 31 and 51 respectively. Thus, if the codereceived by the control means 61 from the photoelectric devices 9 to 13indicates that the body profile is such that the cam member 15 should bein the position 15a, FIG. 2, and that the cam member 27 should be in theposition 27a then a code converter or translator in the control means 61will provide signals on the leads 63 and 64 resulting in the operationof the cylinders 22 and 30. It is, of course, possible for a sprayingprogramme to begin with one particular cam profile arrangement and foran additional photocell or other detector to be positioned to indicatethat there is a change of profile before the programme has finished. Insuch a situation it is possible, by feeding the further information fromthe additional photocell to the control means to arrange that the codeconverter in the control means modifies its output and varies the camprofile accordingly. Alternatively, provision for this change may beprogrammed into the control arrangement 61 according to a profileoriginally recognized by the photoelectric devices so that the changeoccurs after a given time interval from the beginning of spraying. Afurther control signal may also be provided from the control arrangement61 to operate a cylinder for positioning the pivot 50 vertically asmentioned above. Instead of cylinders, other well known positioningmeans, for example rack and pinion and ratchet and pawl mechanisms, maybe used.

As has been mentioned above, other means of control of the cam operatingcylinders may be provided, for example a code may be set up on thehanger or truck, not shown, carrying the body which can be read, forexample, mechanically and the control means may be programmed to operatethe cylinders accordingly. Alternatively, the coded information may beread in the control arrangement 61 from a punched tape, which has beencoded in sequence, in synchronism with the approach of a respective bodyto the spraying apparatus. The coded information on the tape may be fedafter reading directly to the adjusting means or it may be converted asrequired.

Referring to FIGS. 7, 8 and 9 there are shown diagrammaticrepresentations of longitudinal sections through a spray gun guidingarrangement at different levels within the side unit 2. In each of therepresentations the spray gun 4 is shown attached to and freelypivotablc upon an arm 70 which is slidingly arranged within guidebearings 71 and 72. 'Ihe arm 70 is coupled via a U-shaped bracket 73 toa guide block 74 which runs on a rod 75. The whole of the assembly formsa part of a carriage which is reciprocated vertically within the sideunit 2. Attached to the carriage there is an air cylinder 77 having apiston indicated at 78 and a piston rod 79 to which there is pinned astop collar 81 and which carries, freely pivoted at its end, an arm 82carrying a bracket 83 pivoted at 83a attached to the spray gun 4.

The arm 70 carries a roller 84 at its end opposite to that attached tothe gun 4 and the roller 84 moves in the U-shaped channel section of thecam members previously described upon the cam track indicateddiagrammatically at 85.

The arrangement is such that during normal spraying the gun 4 is heldhorizontally. This result is obtained by introducing air into thecylinder 77 on the piston rod side of the piston thereby the stop collar81 holds the roller 84 against the cam track 85 at a reasonably lowpressure so that the gun 4 is held in a horizontal position and thepiston is displaced by the same amount as the spray gun 4 and the roller84. In the two positions illustrated in FIGS. 7 and 8 the effect of thisaction which results in the gun following both the cam and the profileof the surface being sprayed while remaining horizontal can be clearlyseen.

In the illustration shown in FIG. 9 the painting of the body is finishedand the gun and carriage assembly have reached the bottom of theirtravel in the side unit and are at rest. In this position it may benecessary to purge the gun of fluid within it and in order to performthis operation the air pressure in the cylinder 77 is reversed to urgethe piston in the opposite direction and the piston rod 79 moves out ofthe cylinder and causes the spray gun to be tilted forwards so that thepurged liquid enters into a spray booth tank, not shown, provided forthe purpose.

I claim:

1. Apparatus for coating surfaces of a succession of articles ofdifferent shapes and sizes by a spray gun reciprocable along a path in afirst plane during movement of the surfaces past the gun-along a path ina second plane at right angles to said first plane, comprising sensingdevices located along the path of the articles and operable to sense theshape and size of the articles, a cam formed by at least twoprofile-forming members supported for movement relative one to the otherto vary the profile of the cam and to control the movements of the gunin said first plane, profile-forming member adjusting means, and controlmeans connected with said sensing devices and said profile-formingmember adjusting means and operable to actuate the profile-formingmember adjusting means to vary the profile of the cam according to theform of the surface to be sprayed during reciprocation of the spray gunto maintain the position of emission of liquid from the spray gunsubstantially at a predetermined distance from the surface beingsprayed.

2. Apparatus according to claim 1, wherein the profile-forming memberseach include a U-section channel, and a cam profile-forming stripextending lengthwise of the bases of the U-section channels, saidchannels being pivoted one to another and movable about their pivots bythe adjusting means to vary the profile formed by the strip and toeffect curving of the strip between adjacent ends of the channels.

3. Apparatus according to claim 1, wherein there are first and secondprofile-forming members each consisting of a U-section channel, and acam profile-forming strip extending lengthwise of the bases of theU-section channels, the channel of the second member being straightalong the length thereof and the channel of the first member having astraight portion terminating in a curved portion adjacent one end of thechannel of the second member, the adjacent ends of the channels beingsecured to brackets pivotable about a fixed pivot and the ends of thechannels remote from each other being connected to said adjusting means.

4. Apparatus according to claim 1, wherein there are first, second, andthird profile-forming members each consisting of a U-section channel,each said channel being straight along the length thereof, a camprofileforming strip extending lengthwise of the bases of the channels,arms secured to opposite ends of the channels of the second member andextending in opposite directions at right angles thereto, a rocking armrockable about a pivot therefor, said rocking arm carrying pivots at theopposite ends thereof and having said arms pivoted on said pivots, andbrackets secured to the ends of the channels of the first and thirdmembers adjacent the opposite ends of the channel of the second member,said brackets being pivoted one on each of the pivots carried by therocking arm and the ends of the channel of the first and third membersremote from the channel of the second member being connected to saidadjusting means.

5. Apparatus according to claim 4, including further adjusting means forrocking the rocking arm about its pivot.

6. Apparatus according to claim 2, wherein the adjusting means includesfluid-operated cylinders having pistons connected to the pivotable partsof the cam structure. 7

7. Apparatus according to claim 3, wherein the adjusting means includesfluid-operated cylinders having pistons connected to the pivotable partsof the cam structure.

8. Apparatus according to claim 4, wherein the adjusting means includesfluid-operated cylinders having pistons connected to the pivotable partsof the cam structure.

9. Apparatus according to claim 5, wherein the adjusting means includesfluid-operated cylinders having pistons connected to the pivotable partsof the cam structure.

10. Apparatus for coating surfaces of a succession of articles ofdifferent shapes and sizes by a spray gun reciprocable along a firstpath in a first plane during movement of the surfaces past the gun alonga path in a second plane at right angles to said first plane, comprisingin combination:

sensing means located along the path of the articles for sensing thesize and shape of the articles;

a spray gun and means for moving said spray gun along said first path;

variable profile cam means disposed along said first path and engaged bysaid means for moving the spray gun for controlling in and out movementsof the gun relative to said second plane as it is moved along said pathin said first plane; and

control means for varying the profile of said cam means in accord withthe size and shape of the articlc sensed by said sensing means tomaintain said spray gun substantially at a predetermined distance fromthe surface of an article being sprayed.

1. Apparatus for coating surfaces of a succession of articles ofdifferent shapes and sizes by a spray gun reciprocable along a path in afirst plane during movement of the surfaces past the gun along a path ina second plane at right angles to said first plane, comprising sensingdevices located along the path of the articles and operable to sense theshape and size of the articles, a cam formed by at least twoprofile-forming members supported for movement relative one to the otherto vary the profile of the cam and to control the movements of the gunin said first plane, profile-forming member adjusting means, and controlmeans connected with said sensing devices and said profile-formingmember adjusting means and operable to actuate the profile-formingmember adjusting means to vary the profile of the cam according to theform of the surface to be sprayed during reciprocation of the spray gunto maintain the position of emission of liquid from the spray gunsubstantially at a predetermined distance from the surface beingsprayed.
 2. Apparatus according to claim 1, wherein the profile-formingmembers each include a U-section channel, and a cam profile-formingstrip extending lengthwise of the bases of the U-section channels, saidchannels being pivoted one to another and movable about their pivots bythe adjusting means to vary the profile formed by the strip and toeffect curving of the strip between adjacent ends of the channels. 3.Apparatus according to claim 1, wherein there are first and secondprofile-forming members each consisting of a U-section channel, and acam profile-forming strip extending lengthwise of the bases of theU-section channels, the channel of the second member being straightalong the length thereof and the channel of the first member having astraight portion terminating in a curved portion adjacent one end of thechannel of the second member, the adjacent ends of the channels beingsecured to brackets pivotable about a fixed pivot and the ends of thechannels remote from each other being connected to said adjusting means.4. Apparatus according to claim 1, wherein there are first, second, andthird profile-forming members each consisting of a U-section channel,each said channel being straight along the length thereof, a camprofile-forming strip extending lengthwise of the bases of the channels,arms secured to opposite ends of the channels of the second member andextending in opposite directions at right angles thereto, a rocking armrockable about a pivot therefor, said rocking arm carrying pivots at theopposite ends thereof and having said arms pivoted on said pivots, andbrackets secured to the ends of the channels of the first and thirdmembers adjacent the opposite ends of the channel of the second member,said brackets being pivoted one on each of the pivots carried by therocking arm and the ends of the channel of the first and third membersremote from the channel of the second member being connected to saidadjusting means.
 5. Apparatus according to claim 4, including furtheradjusting means for rocking the rocking arm about its pivot. 6.Apparatus according to claim 2, wherein the adjusting means includesfluid-operated cylinders having pistons connected to the pivotable partsof the cam structure.
 7. Apparatus according to claim 3, wherein theadjusting means includes fluid-operated cylinders having pistonsconnected to the pivotable parts of the cam structure.
 8. Apparatusaccording to claim 4, wherein the adjusting means includesfluid-operated cylinders having pistons connected to the pivotable partsof the cam structure.
 9. Apparatus according to claim 5, wherein theadjusting means includes fluid-operated cylinders having pistonsconnected to the pivotable parts of the cam structure.
 10. Apparatus forcoating surfaces of a succession of articles of different shapes andsizes by a spray gun reciprocable along a first path in a first planeduring movement of the surfaces past the gun aloNg a path in a secondplane at right angles to said first plane, comprising in combination:sensing means located along the path of the articles for sensing thesize and shape of the articles; a spray gun and means for moving saidspray gun along said first path; variable profile cam means disposedalong said first path and engaged by said means for moving the spray gunfor controlling in and out movements of the gun relative to said secondplane as it is moved along said path in said first plane; and controlmeans for varying the profile of said cam means in accord with the sizeand shape of the article sensed by said sensing means to maintain saidspray gun substantially at a predetermined distance from the surface ofan article being sprayed.